I have updated my Fx 3.5 list of dlls with one more: Microsoft.VisualC.STLCLR.dll.

As its name suggest, this is an assembly for C++ developers. To be clear, it is of no use to C#/VB developers since it is unusable without including the STL/CLR header. The idea is that if you are comfortable with the C++ Standard Template Library (STL) then you can still use the STL from your C++/CLI code. At the same time, it lets you port your existing unmanaged C++ that has investments in STL, to managed C++ without having to re-implement the STL portions – they just work since the STLCLR collections are compatible with the Generic .NET Collections!